Method and device for the production of curved thread-reinforced tubular structures

ABSTRACT

A method for the production of curved thread-reinforced tubular structures composed of rubber layers and of strengthening layers and an accompanying device. In one aspect, the method includes the application of a first rubber layer to the circumference of mandrels driven forward in a feed direction (X) and winding on of a multiplicity of parallel reinforcing threads, having defined thread angles (α) with respect to the feed axis (x), by means of a bobbin creel, to form a first thread ply. The mandrels are led through a rotating deflection element surrounding the mandrels and the reinforcing threads are guided so as to be distributed on the inner circumference. An application of a covering rubber layer may be performed (after the optionally multiple execution of the previous steps, alone or in combination). The mandrels are led through the deflection element of the bobbin creel eccentrically in the region of the deflection element.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to a method for the production of curvedthread-reinforced tubular structures and a device for such production.

[0003] 2. Background Description

[0004] Curved thread-reinforced tubular structures may be used inautomobile applications such as, for example, pneumatic springs of motorvehicles. A generic production method and device for curvedthread-reinforced tubular structures are known, for example, from DE 2545 058 C3. In this case, mandrels are guided concentrically by the axisof rotation of a deflection element, so that a constant thread angle,distributed over the circumference, is ensured.

[0005] To improve the pneumatic spring properties of the tubularstructures, it is known from DE 196 14 476 A1 and EP 0 285 726 B1 tovary the thread angle over the length of the pneumatic springs. Due tothe varied thread angle in the axial direction of the pneumatic springbellows, the latter has a differing outside diameter according to thethread angle, so that the rolling behavior and the air pressures can beadapted to the respective requirements involved in the installation andoperation of the pneumatic spring bellows in a pneumatic spring.

[0006] The winding of reinforcing threads on to mandrels guided in afeed direction, with a rubber layer extruded on them, is known, forexample, from DE 198 46 852 C2. In this case, the reinforcing threadsare guided in a deflection element on the inner circumference of thedeflection element with a very small gap with respect to the mandrel.The reinforcing threads are guided to the outer circumference of themandrel or of the rubber layer located on it by means of guidesdistributed equidistantly on the inner circumference of the deflectionelement. In this situation, the deflection element rotates at a speedcorresponding to a required thread angle with respect to the feeddirection.

[0007] When, for example, the pneumatic springs are installed invehicles, the installation situation is sometimes so unfavorable thatcurved pneumatic springs have to be used. Curved tubular structures areconventionally produced by straight thread-reinforced tubular portionsbeing prestressed into a curved shape and then vulcanized. Such a methodis described, for example, in DE 25 45 058 C3. One disadvantage,however, is that the run of the reinforcing threads during production isnot adapted to the curved shape. During prestressing, a displacement ofthe reinforcing threads which is detrimental to the quality of the finalproduct then sometimes occurs. Moreover, only a complete curvature ofthe tubular portion is possible, but not the production of selectedcurved regions.

SUMMARY OF THE INVENTION

[0008] The invention provides a method and a device for production ofcurved thread-reinforced tubular structures composed of rubber layersand of strengthening layers, so that it is possible to generate curvedportions at low outlay during a continuous production process.

[0009] In one aspect, the invention includes the steps:

[0010] application of a first rubber layer to the circumference ofmandrels driven forward in a feed direction (X);

[0011] winding on of a multiplicity of parallel reinforcing threads,having defined thread angles with respect to the feed axis, by means ofa bobbin creel, to form a first thread ply, the mandrels being guided bya rotating deflection element surrounding the mandrels and guiding thereinforcing threads so as to be distributed on the inner circumference;

[0012] application of a covering rubber layer after the optionallymultiple execution of the previous steps, alone or together; and

[0013] leading the mandrels through the deflection element of the bobbincreel eccentrically in the region of the deflection element.

[0014] In another aspect of the invention, the method includes, forexample,

[0015] leading at least one mandrel through a deflection element of abobbin creel in a feed direction, offset from a central longitudinalaxis of the deflection element; and

[0016] winding a multiplicity of parallel reinforcing threads on the atleast one mandrel as the mandrel is led through the deflection elementresulting in defined thread angles (α) with respect to a feed axis toform a tubular structure having a curvature.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The foregoing and objects, aspects and advantages will be betterunderstood from the following detailed description of embodiments of theinvention with reference to the drawings, in which:

[0018]FIG. 1 shows a device for the production of curvedthread-reinforced tubular structures with an eccentric lead through of amandrel through a deflection element; and

[0019]FIG. 2 shows a curved pneumatic spring with curved pneumaticspring bellows.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0020] The invention relates to a method for the production of curvedthread-reinforced tubular structures and a device for such production.In one implementation, the tubular structure is composed of rubberlayers and of strengthening layers. In one aspect of the invention,thread-reinforced tubular structures made in accordance with theinvention may be used, for example, as pneumatic spring bellows forpneumatic springs of motor vehicles. In this type of application, thethread-reinforced tubular structures contain a multiplicity ofreinforcing threads which lie closely next to one another at equidistantintervals, in order to be capable of withstanding the high pressure ofthe pneumatic spring.

[0021] In contrast to the conventional concentric lead through of themandrels through the deflection element and to the resulting equalthread angles over the circumference, an eccentric lead through of themandrels through the deflection element is provided herein. That is, inthe invention mandrels are guided eccentrically or offset from a centrallongitudinal axis through a deflection element of a bobbin creel in theregion of the deflection element. For this purpose, the inside diameterof the deflection element is correspondingly larger than the diameter ofthe mandrel covered with at least one rubber layer.

[0022] In one aspect of the invention, the thread angle correspondsdirectly to the distance of the deflection element from the mandrel, sothat, when the mandrels are led through eccentrically, different threadangles are produced over the circumference of the mandrels. By contrast,the thread angles of a respective circumferential position remain thesame over the length of the mandrels.

[0023] Due to the different thread angles over the circumference, thetubular structure undergoes a curvature which is establishedautomatically after the thread-reinforced tubular structure has beendrawn off from the mandrels and after subsequent vulcanization.Advantageously, therefore, it is necessary merely to lead 5 the mandrelsthrough the deflection element eccentrically, in order to produce curvedtube-like structures, without further steps, such as the conventionalrequired bending of the structures being necessary before vulcanization.Moreover, the advantage of the method according to the invention isthat, by a variation of the eccentric lead through and, if appropriate,centric lead through in part regions, selected portions of the tubularstructure can be provided with defined curvatures during the continuousproduction process.

[0024] For the eccentric lead through of the mandrels through therotating deflection element, either the guide of the mandrels may bedisplaced transversally to the feed direction about a position shiftedwith respect to the concentric lead through of the mandrels through thedeflection element. Alternatively or additionally to this, thedeflection element, together with the bobbin creel, may also bedisplaced transversely to the feed direction from a position shiftedwith respect to the concentric lead through of the mandrels through thedeflection element. In this case, displacement may take place in thehorizontal and/or the vertical direction.

[0025] The invention is achieved, furthermore, by means of the devicefor the production of curved thread-reinforced tubular structures byguide means for guiding the mandrels eccentrically through thedeflection element of the bobbin creel in the region of the deflectionelement. In the device, at least one bobbin creel which has a rotatabledeflection element surrounds mandrels capable of being driven forward ina feed direction and which guides reinforcing threads so as to bedistributed on the inner circumference.

[0026] So, either of the guide means of the device may cooperate withthe mandrels, in order to displace the mandrels transversally to thefeed direction about a position shifted with respect to the concentriclead through of the mandrels through the deflection element.Additionally or alternatively to this, the guide means may alsocooperate with the bobbin creel, in order to displace the bobbin creeltransversally to the feed direction about a position shifted withrespect to the concentric lead through of the mandrels through thedeflection element.

[0027]FIG. 1 illustrates a detail of a device according to the inventionfor the production of curved thread-reinforced tubular structures, inwhich one or more plies of rubber layers and of strengthening layers inthe form of thread contextures are applied to a mandrel 1. The rubberlayers are applied to the mandrel and/or a thread ply, for example, byextrusion in a known manner.

[0028] The mandrels 1 are advanced in a continuous process in a feeddirection X through successively arranged extrusion devices for applyingthe rubber layers and bobbin creels for applying the thread plies. Thebobbin creels generally shown at “C”, in this aspect, have a deflectionelement 2 which rotates in the direction of rotation R and by means ofwhich reinforcing threads 3 are applied to the mandrel 1 at a threadangle α with respect to the feed direction X. The thread angle α isdependent on the feed speed of the mandrel 1 and on the gap S betweenthe inner circumference of the deflection element 2 and the adjacentouter circumference of the mandrel 1.

[0029] According to the invention, in this case, the mandrel 1 is ledthrough the deflection element 2 so as to be offset eccentrically by theamount of a distance “a” from the axis of rotation of the deflectionelement 2. The result of this is that the reinforcing threads 3 areapplied in the circumferential region of the mandrel 1 having thesmaller gap S at a thread angle α₁ other than in the circumferentialregion of the mandrel 1 having the larger gap S₁. However, duringconstant displacement of the mandrel 1 about the axis of rotation at thedistance “a”, for each circumferential region the thread angle a remainsthe same over the length of the mandrel 1.

[0030] During the production of the thread-reinforced tubularstructures, the eccentric displacement “a” may be adapted in any desiredway. Also, part regions having the same thread angle α may also beprovided over the circumference by the mandrel 1 being led centricallythrough the deflection element 2. Complicated curved shapes of thethread-reinforced tubular structure can thereby be produced.

[0031] Due to the different thread angles α over the circumference ofthe thread-reinforced tubular structure, under pressure a curved shapeis formed in such a way that a small radius is obtained in the region ofthe smaller thread angles α₁ and a large radius is obtained in theregion of the large thread angles α₂.

[0032]FIG. 2 illustrates a curved pneumatic spring 4 with a pneumaticspring bellows 5 which is drawn over a piston 6 and a cover 7. Thecurved shape of the pneumatic spring bellows 5 is imparted in that thethread angle α of the reinforcing threads 3 is different, distributedover the circumference. Thus, the thread angle α₁ in the region of thesmaller radius on the left-hand side is smaller than the thread angle α₂on the right-hand side having the larger radius.

[0033] Pneumatic springs 4 of this type may also be used in installationsituations where, for example because of the cardanic axle mounting ofthe pistons, a curved shape of the pneumatic springs 4 is necessary. Theresulting concertina widths between the pneumatic spring bellows 5 andthe piston 6 are optimally designed for the corresponding cardanic axlemounting by virtue of the adaptation of the thread angles by means ofthe method according to the invention, so that the useful life of thepneumatic springs 4 is increased. Moreover, curved pneumatic springs 4can be adapted more effectively to the confined construction spaces invehicles, and the dynamic properties and therefore the drivingproperties of a vehicle can be improved.

[0034] While the invention has been described in terms of preferredembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theappended claims.

1. A method for production of curved thread-reinforced tubularstructures composed of rubber layers and of strengthening layers,comprising the steps of: applying a first rubber layer to acircumference of mandrels driven forward in a feed direction (X);winding on a multiplicity of parallel reinforcing threads, havingdefined thread angles (α) with respect to a feed axis, by means of abobbin creel, to form a first thread ply, the mandrels being led througha rotating deflection element surrounding the mandrels and guiding thereinforcing threads so as to distributed. on the inner circumference;applying a covering rubber layer, wherein the mandrels are led throughthe deflection element of the bobbin creel eccentrically in the regionof the deflection element.
 2. The method as claimed in claim 1, furthercomprising displacing a guide of the mandrels transversally to the feeddirection (X) about a position shifted with respect to a concentric leadthrough of the mandrels through the deflection element.
 3. The method asclaimed in claim 1, fuirther comprising displacing the deflectionelement, together with the bobbin creel, transversely to the feeddirection (X) from a position shifted with respect to a concentric leadthrough of the mandrels through the deflection element.
 4. The method asclaimed in claim 1, wherein the applying the covering of the rubberlayer is provided after optionally multiple execution of at least one ofthe applying a first rubber layer and the winding steps.
 5. The methodas claimed in claim 1, further comprising cooperating the guide with themandrels in order to displace the mandrels transversally to the feeddirection (X) about a position shifted with respect to a concentric leadthrough of the mandrels through the deflection element.
 6. A device forthe production of curved thread-reinforced tubular structures,comprising: at least one bobbin creel which has a rotatable deflectionelement which surrounds mandrels being driven forward in a feeddirection (X) and which guides reinforcing threads so as to bedistributed on the inner circumference; and adjustable guide means forleading the mandrels through the deflection element of the bobbin creeleccentrically in the region of the deflection element.
 7. The device asclaimed in claim 6, wherein the guide means cooperate with the bobbincreel in order to displace the bobbin creel transversely to the feeddirection (X) about a position shifted with respect to the concentriclead through of the mandrels through the deflection element.
 8. Thedevice as claimed in claim 6, wherein an inside diameter of thedeflection element is correspondingly larger than a diameter of themandrel covered with at least one rubber layer.
 9. A method forproduction of curved thread-reinforced tubular structures, comprisingthe steps of: leading at least one mandrel through a deflection elementof a bobbin creel in a feed direction, offset from a centrallongitudinal axis of the deflection element; and winding a multiplicityof parallel reinforcing threads on the at least one mandrel as themandrel is led through the deflection element resulting in definedthread angles (α) with respect to a feed axis to form a tubularstructure having a curvature.
 10. The method as claimed in claim 9,further comprising the steps of: applying a rubber layer to acircumference of at least one mandrel driven forward in a feed direction(X); and applying a covering rubber layer to the rubber layer.
 11. Themethod as claimed in claim 9, wherein the at least one mandrel is ledthrough the deflection element eccentrically in the region of thedeflection element.
 12. The method as claimed in claim 11, wherein thethread angles correspond directly to a distance of the deflectionelement from the at least one mandrel so that when the at least onemandrel is led through the deflection element different thread anglesare produced over a circumference of the at least one mandrel.
 13. Themethod as claimed in claim 9, wherein the winding on a multiplicity ofparallel reinforcing threads forms a tubular structure whichautomatically undergoes a curvature after the multiplicity of parallelreinforcing threads are drawn off from the at least one mandrel.
 14. Themethod as claimed in claim 13, further comprising vulcanizing themultiplicity of parallel reinforcing after it is drawn from the at leastone mandrel.
 15. The method as claimed in claim 9, further comprisingvarying the offset lead through of the at least one mandrel at selectedportions to define curvatures of a resultant tubular structure.
 16. Themethod as claimed in claim 15, further comprising varying the leadthrough of the at least one mandrel at selected portions to beconcentric with the deflection element.
 17. The method as claimed inclaim 9, wherein the lead through of the at least one mandrel throughthe deflection element is provided by at least one of: displacing guidesof the mandrels transversally to the feed direction about a positionshifted with respect to a concentric lead through of the at least onemandrel through the deflection element; and displacing the deflectionelement, together with the bobbin creel, transversely to the feeddirection from a position shifted with respect to the concentric leadthrough of the at least one mandrel through the deflection element. 18.The method as claimed in claim 9, wherein the at least one mandrel isadvanced in a continuous process in a feed direction X throughsuccessively arranged extrusion devices.
 19. The method as claimed inclaim 9, wherein the thread angles are dependent on a feed speed of theat least one mandrel and a gap between an inner circumference of thedeflection element and an adjacent outer circumference of the at leastone mandrel.
 20. The method as claimed in claim 9, wherein: a smallergap between the circumferential region at least one mandrel and thedeflection element results in thread angles α₁; a larger gap between thecircumferential region of the at least one mandrel and the deflectionelement results in thread angles α₂; and a small radius is obtained in aregion of the smaller thread angles α₁, and a large radius is obtainedin a region of the large thread angles α₂.